Types of Phones | Voice Communications

Although different types of phones require the same basic system components to allow a standard level of operation with the cellular network, significant differences between mobile, transportable, and handheld units can most often create the major decision points as to which is right for any specific application.

Mobile units

Mobile units are permanently installed in a vehicle, usually by the provider of the equipment, and typically consist of "bolted-in" components. This type of installation generally involves installing the equipment and routing the cables so that they will not be damaged as part of the normal use of the vehicle. Cables and equipment are placed and secured so that cargo and people cannot easily displace them. Since the system is subject to continuous vibration and the rough jolts caused by road hazards, potholes, and other everyday occurrences, the installation should typify equipment that might be factory installed, and some manufacturers have in fact offered this as an option. Since space in the driver's area is at a premium, the handset is typically mounted to be accessible to the driver, and the other components can be installed elsewhere in the car.

As noted, mobile units utilize the vehicle's 12-V DC battery as a power source. Mobile phone transmitters generally operate at a full 3-W level, the maximum for cellular units. This provides the best available overall performance in terms of signal quality and physical range of use. The transmitter output power level is very dependent upon a strong input power source.

Transportable units

Transportable phones comprise the same components as the mobile telephones but are packaged as a single unit. The transportables are generally used in vehicles by plugging them into the cigarette lighter outlet to obtain a reliable power source, and also by connecting to either a temporary magnet-mount antenna on the car roof or to a permanently installed antenna. The unit is not bolted to the vehicle but is commonly placed on the seat. Performance of these transportable units can rival a mobile unit, especially since the critical power source and antenna system components are virtually identical. By disconnecting the power and the antenna, the unit can be carried from the vehicle to be used in another car or to be used as a self-contained system through use of an integral rechargeable battery and a small antenna. The units ordinarily weigh about five pounds, but the battery capabilities and battery weight increase in a directly proportional manner. In this portable configuration outside a car, the system becomes subject to limitations of the battery.

All phones—mobile, portable, and handheld—draw increased levels of power while in use, and lower levels when in standby mode (on-hook). The battery must be either replaced or recharged after a few hours of continuous talk time, or following a somewhat greater number of hours of combined talk and standby time. Although portables are available that offer full 3-W transmit power, use of reduced power levels of less than 3-Wcan enable some of these phones to operate over an extended period of time, given the same battery capability. The antenna, which now has no metal vehicle underneath to act as a performance-enhancing ground plane, performs adequately but certainly not with the range of a car-mounted antenna. These units are especially suited to field use where, even though the phone might remain in a fixed location, no conventional telephone service exists. In such applications, auxiliary power might be available to augment the battery in a configuration similar to that of a mobile installation.

Handheld units

Handheld units range from those that weigh approximately a pound to tiny pocket phones that can weigh less than 4 ounces. These most closely resemble handheld two-way radios with extendible or flexible rubber antennas and small batteries contained within the handset. The smallest of these, the microminiature pocket phones, represent the ultimate in portability, but at the expense of battery life and transmit power levels. Talk time from a single battery can be as little as an hour or two, with standby time of 8 to 36 hours. Some units can operate with disposable alkaline batteries as well as, or instead of, the rechargeable nickel-cadmium or nickel-metal hydride battery packs in order to improve the phone's weight-to-performance ratio and to free the user from the constraint of maintaining a supply of recharged battery packs. Handheld units generally operate at transmit power levels of approximately a half-watt. This certainly limits their range and capabilities as compared to a three-watt mobile or transportable unit, but they do perform well as long as they are used in reasonable proximity to the main coverage areas of most cellular networks.

Wearable units

The ultimate communications device for mobile professionals is the cellular phone that can be worn as an accessory on clothing. Motorola's StarTAC phone, for example, may be worn easily and unobtrusively by both men and women on the go. Such units weigh in at 3.1 ounces. When opened to its full size, the StarTAC phone forms to the face to maintain the familiar ear-to-mouth ratio. When folded, the StarTAC phone can be worn fashionably as an accessory.

Despite their light weight and compact design, such phones are capable of advanced features. Motorola's StarTAC 8600 Series of VoiceNote Cellular Phones, for example, feature an answering machine/voice recorder with up to 4 minutes of record time. Other phone features available with the StarTAC phone are: a "Smart" Button, which allows for simplified one-handed use of the phone; silent vibration alert for incoming calls; and a headset jack for hands free conversations. A 1.9-MHz GSM (Global Systems for Mobile communication) version of the phone—the StarTAC Select Series—weighs slightly more at 3.5 ounces, but incorporates a full-size SIM (Subscriber Identity Module) card.

Many value-added services will be aided by a unique feature of GSM's SIM card. This removable "smart card" uses a microchip to store the owner's billing data, special features, speed dial numbers, and other vital information, and can be used in any compatible handset. The SIM card allows for over-the-air activation, contributes to secure network access, and facilitates roaming among international locations.

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